Casting of wire-inserted aluminum alloy composite strip was tried using a downward melt drag twin roll caster. The process of the present study was very simple. The coil of the steel wire was only attached to the melt drag twin roll caster in order to cast the wire-inserted strip. The steel wire, which diameter was 0.3 mm and 0.6 mm, was inserted at the inside and at the surface of the aluminum alloy strip. Strip casting and wire-inserting could be carried out at the same time. The wire-inserted strip could be cast without gap between the wire and the strip, when casting condition was proper. The roll speed and the diameter of the wire affected the gap between the wire and the strip. The wire-inserted strip could be carried out the cold rolling. The reduction of wire was almost same as the reduction of the strip. The gap between the wire and the strip could be improved by the rolling. The steel wire did not react with the aluminum alloy of the strip.

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Mechanical properties and fatigue properties of magnesium alloy die castings AZ91D and rolled magnesium alloy AZ31B are investigated by tensile test, fracture toughness test and fatigue crack propagation test, (1) There is no effect of metal flow direction in AZ91D. (2) AZ91B has large aerotropy which the strength of extrusion direction is larger. (3) The 0.2% proof stress of AZ91D is better than AZ91B. (4) The fracture toughness of the AZ91B is better than AZ91D. (5) There is almost no difference of fatigue crack growth characteristics in second and third region of ΔK between AZ9ID and AZ31B.

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Effect of casting defect and stress ratio on fatigue life under uniaxial cyclic load are investigated for products made of aluminum alloy die castings. The main results are as follows, (1) Fatigue limit becomes small as a defect becomes large. Efect of casting defect can be quantified by using the stress intensity factor range. (2) Minimum community stress intensity factor range which does not cause fatigue destruction and which are conditions is changed by the stress ratio, and is not an absolute value.

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Mechanical and fatigue properties of magnesium alloy die castings AZ91D and AM60B are investigated by tensile test, fracture toughness test and fatigue crack propagation test. It is obtained the tensile strength and 0.2% proof stress of AZ91D is better than AM60B. The fracture toughness of AM60B is better than AZ91D. The fatigue properties of AZ91D and AM60B are almost the same in all area. The direction of metal flow doesn't affect every characteristic. Metal flow and solidification during casting process is examined by FEM simulation method.

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This paper focuses on the mushy forming process of the low carbon steel. The mushy state behavior and the mushy extrusion property of the low carbon steel S20C are investigated in particular. At firstly cooling curve of the investigated steel is measured by thermal analysis method in order to make a mushy/semi-solid temperature range clear. The Internal structures obtained at mushy temperature of S20C exhibited globular internal structure, just as the mushy/semi-solid aluminum alloys or magnesium alloys internal structure did. The extrusion tests are carried out with different billet temperatures in order to investigate the possibility of mushy extrusion.

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Influence of water embrittlement effect of several kinds of ductile irons were studied from such view points as tensile strength, elongation, energy to failure, kind of wetting agent, and effect of pre-straining. The ADI and the Quenched & Tempered specimens showed a considerable embrittlement effect in many view points. The CT specimen with a hole which had been pre-strained to the middle point between the dry and the wet failure points showed a higher failure point than the wet failure point.

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Fatigue strength of high-strength sheet steel is deteriorated by piercing, and coining to the pierced hole improves the fatigue strength, which makes an edge of hole smooth and introduces compressive residual stress at the edge of hole. In this report, using FEM analysis, the behavior of material at the edge of hole during coining is investigated. As a result, radial deformation of the hole has a large effect on the behavior of residual stress after coining and improvement of fatigue strength can be explained by this compressive residual stress.

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Pin-on-disk type friction and wear tests of a mild steel in contact with itself were carried out under unlubricated conditions in wet air to investigate the effects of changes in load on the transition between severe and mild wear. After the formation of heavily work-hardened wear surfaces under severe wear at first, the surfaces are oxidized under mild wear conditions at a low load, and then the wear mode changes to quasi-mild wear of low rate even under a high load at the next steps.

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In order to study the effect of density, contact fatigue tests were carried out on two types of sintered alloys. A higher contact fatigue strength was observed for both the material with increase in density. This may due to the difference of Young's modulus of each material. Fatigue strength was affected by lubricant condition at the contact point. Cracking occurred below the specimen surface. Depth of crack almost coincides with the position of maximum shearing stress by contact stress.

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Wet rolling contact fatigue testing of ductile iron was carried out. Initiation and propagation of surface crack and subsurface crack were observed. The results are summarised as follows: (i) Surface crack was arrowhead-like; (ii) Surface crack tended to initiate from the edges of spheroidal graphite; (iii) Most of subsurface cracks propagated at an angle of about 20° to contact surface, while some of them propagated parallel to contact surface in depth of 25 μm from surface.

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Bearing tests were carried out under various loading conditions for SUJ2, and the morphologies of flaking failures caused by rolling contact fatigue were investigated by surface and cross-sectional observation. It was found that the depth of flaking failure tended to be smaller than that was estimated by the conventional method based on the maximum shearing stress. A new method to estimate the depth of flaking failure based on stress intensity factor K_<II> of subsurface crack was proposed in this paper. It was confirmed that the depth estimated by this method was closer to the actual depth than estimated by conventional method. Using this method, the length and width of flaking failures were also investigated.

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The effect of crack face friction on surface crack growth of Si_3N_4 ball bearings was investigated under rolling contact fatigue (RCF). The tests were carried out by using a thrust-type RCF machine. Small surface cracks were made by using a Vicker's indenter and their lengths were measured during the tests. The cracks grew stably during the tests. Stress intensity factors were calculated by taking crack face friction into consideration, and the effect of the friction on surface crack growth was investigated. It was found that crack face friction doesn't affect K_<Imax> or ΔK_<III>, but ΔK_<II> is affected in the middle range of crack lengths.

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In order to clarify the mechanism of flaking which is generated on the race and bearing of the ceramics, rolling fatigue tests under lubricated ball-plate contact were carried out on the smooth HIP-Si_3N_4 race and the pre-cracked HIP-Si_3N_4 race, and surface crack and flaking shape were respectively observed by the optical microscope and the laser microscope. As a result, it was found that the fatigue life of race and bearing depended on a load, and the fatigue life of pre-cracked race is 1〜2% in that of the smooth race. Furthermore, the origins of flaking were respectively surface defect for smooth race, cone crack for pre-cracked race with ring crack and the indentation for pre-cracked race with knoop.

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Damage in rotating contact fatigue was observed in this study. Experiments were carried out by the contact of the specimen of polycarbonate with that of carbon steel S45C on lubricated condition. By this method, damages were concentrated in the polycarbonate, only. When the carbon steel was set to be the drive side, experiment in which the specimens were rotated in the unidirection and experiment in which the rotation's direction changes every 3×10^5time rotational frequency were carried out. In the former case, surface cracks initiated with arrowhead shaped. Then, pits were formed controlling by the maximum principal stress. In the latter case, elliptic pits from the viewpoint of the surface were formed. Then, the cracks grew in the diameter direction from the pits bottom. When the polycarbonate was set to be the drive side, internal cracks initiated by shear mode, then surface layer of the polycarbonate peeled off. From those experiment, it was found that damage mechanisms of contact rotating fatigue changed by the loading conditions. These mechanisms are related to friction of the specimen surfaces and to action of pressure of oil that enter into the crack inside.

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The purpose of this study is to elucidate the validity of a sphere indentation test in order to evaluate the damage in ceramic specimens applied a constant load for a long time. Four points bending tests with a constant load were carried out on silicon nitride specimens for various holding time. After bending tests, sphere indentation tests were done on the specimens to obtain the strength for a ring crack initiation on the surface layer of the specimen. X-ray diffraction method was also used to measure the residual stress of the specimen.

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Scratch tests were carried out on TiC and TiN PVD-coating. Occurrence of AE signal and the change of frictional force during scratch test show local delamination of coating at the critical load, L_c, in agreement with the observation of scratch track on the specimen surface. The critical load, L_c, was obtained as 25 and 70 N for TiC and TiN coatings, respectively. In order to study damage process of coating during scratch test, cross section of scratch track were observed. Cracks perpendicular to the interface were observed in the coating layer on both of TiC and TiN coatings. Local delamination occurred at the edge of scratch track at L_c.

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When solid particles in liquid impact on the material surfaces, part of the surface materials is damaged or removed. This phenomenon is called "Erosion". Erosion raises some serious problem with the pipe bend parts and the valves of piping concerning the mixed tow-phase flow of gases and solid. Paying attention to the results obtained until now, we investigated the wear characteristic from the viewpoint of the shape of solid particles. Concretely, the erosive wear characteristic was evaluated by using the high chromium steel by the conventional experimental technique employed previously.

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"Homogenizer"is a device to obtain homogeneous emulsion without any fluid separation. In our experiments, cocoa powder was dissolved into water as moving fluid and it was repeatedly jetted onto a specimen-surface. The material of specimens is SUS316 for all disks; Flat, Sharp, Screw and Dimple disk-shapes. In screw disk, the more steps are, the longer life span is. As to two-steps of dimple disk, radiated eroded-surface is confirmed.

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A phenomenon that solid particles in mixed liquid and solid collide with the surface of steel materials and do damages on the surface or remove the material from the surface is named slurry erosion. The slurry erosion has caused a serious problem on piping and so on in transportation system of mixed liquid and solid. In this research, the erosive wear has been paid attention to, excluding the corrosion element from the slurry and erosive wear. The slurry erosion is mainly caused by sand and sand is used as impact particles in this research. And various kinds of material are evaluated on their erosion wear characteristic in the same experimental method used before.

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This paper describes effects of oxides whisker addition on tribological properties of a series of Al-Si based films coated by a low pressure plasma spraying. Friction and wear properties of films were evaluated by employing a reciprocating sliding tester under a boundary lubricating condition. The hardness and wear resistance increase with whiskers addition. Mechanisms of improvement by the whisker addition were discussed with analytical results of micro-structure of films and sliding surfaces by using SEM, EPMA and XRD.

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This paper aims at investigating the influences of kinds of work materials on a behavior of crater wear using three kinds of high-speed steel hob substrates in dry hobbing. Experiments were carried out using a fly tool. As a consequence, the following points were clarified : (1) When cutting a SCM415 in the work materials having almost the same hardness tested, the crater wear shows the smallest value using a corresponding to SKH55 coated with (Al,Ti)N. (2) It was suggested that the crater wear reduction is caused by the deposited metal covered on the tool face.

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Effects of the sintering properties and the number of laminated layers on cracking in sintering process were examined by experiment for metal/ceramic graded powder compacts and the internal stresses were estimated by numerical analysis to reveal the condition of crack formation. Cracks on the surface of the top ceramic layer disappeared with reducing the number of the other layers. Although the decrease in sintering rate of the ceramic layer changed the direction of warping, it did not contribute to the suppression of cracking. Diagrams giving the in-plane stress on the surface, produced by mismatch in sintering rate and bending of the layers, were presented as a function of the sintering stress and the viscosity.

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The rate of peritectoid reactions such as FeSi(ε: core)+Fe_2Si_5(α: matrix) → 3FeSi_2(β: rim) in Fe-66.7at%Si alloy are well known to be generally extremely slow. Such extremely slow rate has been said to be because the reaction is a solid state reaction where atomic diffusion rate is extremely slow, or because the atomic diffusion distance of the reactant atoms from the matrix to the reaction interface of core/rim, i.e., the thickness of the rim increases with the progress of the reaction. On the other hand, we have proposed that such slow rate is supposed to be also due to the exhaustion of the diffusion-contributable vacancies in core/rim structure. In this report, the concept and applications of this hypothesis will be explained.

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Characteristics of Mg Based Composite Material via Solid-State Synthesis have been evaluated. Dispersions, Mg_2Si particles, were in-situ synthesized by heating the green compact from the pre-mixed Mg-Si powder at 853K in N_2 gas atmosphere. After heating the compact including Mg_2Si particles, it was consolidated by direct powder forging process. The powder forged Mg composite shows good bonding at the interface between Mg_2Si and the matrix. Mechanical-properties, such as hardness and tensile strength, increase with increase in the Mg_2Si content due to the dispersion strengthening effect.

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Effect of phase change from unstable to stable phase on densification process by pressure sintering was studied using mechanically alloyed powder. Powder mixture of Ti and Si having the composition of Ti-37.5mol%Si were milled for 3600ks. The powder showed homogeneous microstructure and amorphous-like XRD profile. And also 360ks milled powder having (Ti+Si) lamella microstructure was used. Milled powders were vacuum hot pressed at constant heating rate up to 1273K with applying constant pressure of 100MPa, then kept for 10.8ks. It was observed that the sudden increase in density at the temperature range between 840K and 905K. This temperature range showed good agreement with that of the phase formation from unstable to stable phase, Ti_5Si_3. From experiments to measure the thermal expansion of amorphous and elemental compacts and to consider the densification behaviors of heat treated powders, it is presumed that the enhancement of densification during crystallization from amorphous phase is closely related the extra ordinate deformation of amorphous material around the crystalline nucleation.

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This paper describes the newly developed P/M sprockets for silent chain system of DIG (DIRECT INJECTION GASOLINE) engines. The wear of silent chain and sprocket itself is severe. And DIG system sometime generates more carbon soothe than the other engines. So it is necessary to develop new P/M sprocket with high anti-wear characteristics. The combination of warm compacting and high temperature sintering is adopted in this development. Molybdenum-Nickel alloy steel powder is selected as the raw material.

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Consolidation of rapid solidified Fe-Cu powder with severe plastic deformation (SPD) is investigated. Rapid solidified Fe-Cu powder where copper is supersaturated is consolidated with groove rolling at 873K and 973K. Characterizations of the consolidated samples have been done by microstructure observation and tensile testing. The tensile tests are suspended in the various loading point to observe the macrostructures change during loading. Based on the experimental results, deformation and fracture mechanism are discussed.

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In our previous studies on the 4600 steels produced by metal injection molding (MIM) process using mixed elemental powders, the fine heterogeneous microstructure caused by the agglomeration of Ni powders was reported to be significantly effective for the improvement of mechanical properties. This study has been performed to obtain the high densified compacts using the bimodal powders the double pressing and sintering, and moreover to investigate the relationship between the mechanical properties and the heterogeneous microstructure of the compacts (4600 grade, 0.4 mass%C).

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We have developed a composite material of dispersed diamond particles in cemented carbide without using ultra high pressure equipment. The developed diamond dispersed cemented carbide combines the excellent properties of cemented carbide with diamond and also provides 1.5 times improved fracture toughness over that of cemented carbide. They also show 10 times higher wear resistance over that of cemented carbide in a wear resistance test against bearing steel, and 5 times greater grindability than diamond compacts. Because ultra high pressure equipment is not used to produce the developed material, large compacts over 100mm in diameter can be manufactured.

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Borides are promising candidates for wear resistant materials. But poor sinterability and extreme brittleness of borides retarded the fabrication of bulk materials. This paper gives criteria for the development of boride base cermets. Reaction boronizing sintering technique has successfully brought development of Mo_2NiB_2 type ternary boride base cermets. The addition of Cr and V to the cermets changed the boride structure from orthorhombic to tetragonal and resulted in the improvement of mechanical properties and microstructural rifinment. Ni-4.5B-47.9Mo-12.5V-xMn (mass%) model alloys with five levels of Mn content from 0 to 10mass% were prepared to investigate the effects of Mn on the mechanical properties and microstructure of Mo_2NiB_2 base cermets. The transverse rupture strength (TRS) of the cermets depended strongly on the microstructure, which varied significantly with Mn content. The maxmum TRS obtained at 2.5mass%Mn were 3.5GPa with hardness of 87HRA.

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Investigation of an influence of pulse condition on heating rate and a model experiment for estimating interface temperature are done in order to investigate the effect of pulse current on sintering in pulsed current sintering. Using a graphite mold, the heating rate depends on energy by pulsed current, but it is independent of a pulse frequency. In the model experiment using Al ball, variation of the interface temperature with time depends on a pulse frequency. The temperature difference between an interface and an Al body in the case of frequency 2Hz to 100Hz changes similarly, and it is preserved for a long time in comparison with that in the case of DC current.

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When the content of carbon in the Fe phase of liquid phase sintered Fe-Cu alloy is graded by using solid carburization method, the microstructure of the cross section of the sample has characteristic orientated Cu phase. The orientation of the Cu phase has the same direction of carburization, and the area of oriented Cu phase depends on the diffusion distance and the content of carbon. We execute three simulation programs by using modified Potts model and Monte Carlo method. These three simulation programs are: i) solid diffusion of carbon into Fe particles, ii) solution of Fe site into Cu liquid phase and precipitation on Fe-C particle, iii) surface smoothing of Fe-C particles by surface diffusion.

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An ongoing development of structural materials requires much finer and more complex composition of microstructures than ever, and it must accompany, inevitably, a development of processing methods. P/M technology is a candidate for it with its wide applicability to various materials. However, most of current P/M processing use starting materials of 10 μm or more, which is not sufficient to achieve micron or nano microstructures. In the present study, we used High-Speed Centrifugal Compaction Process (HCP) as a new compacting method of fine powders. In HCP, powders are prepared as slips and compacted under high centrifugal force of about 10,000g. A fine (4 μm) stainless steel (SUS316L) powder was successfully compacted by HCP to a green compact with a packing density of 68%. It sintered at low temperature of 1323 K, consisted of homogeneous and fine grains, and showed high tensile strength of 600 MPa. All these positive results were due to the appropriate use of fine powder.

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